With a concern for simplifying the description, the remainder of this document is limited to describing the particular case wherein the radiocommunication device is a GSM radiocommunication terminal. Those skilled in the art will easily extend this knowledge to any other type of radiocommunication terminal.
Conventionally, a GSM radiocommunication terminal cannot access the services of the GSM network without a SIM card. Indeed, a SIM card is a module comprising all of the data concerning the subscriber, i.e. an identity number IMSI (for “International Mobile Subscriber Identity”), an authentication key Ki, as well as algorithms associated with the authentication of the subscriber by the GSM network.
As such, a GSM terminal including a SIM card can transmit voice data and non-voice data to other radiocommunication terminals via the GSM network.
The disadvantages of prior art shall be discussed hereinafter through the particular case wherein a user wants to transmit location information (for example GPS coordinates) during an emergency call.
A motorist who has a GSM terminal (for example a radiotelephone), including a SIM card, can, in the event of a breakdown, call the emergency services by dialing the number 112 (telephone number reserved for emergency calls and valid throughout the entire European Union) or call a breakdown mechanic.
In such a situation, the motorist can also use his GSM terminal to send, in the form of an SMS or calls of the DATA/GPRS type, non-voice data, for example, location information provided by a GPS device for example built into the vehicle. With the sending of this non-voice data, the motorist makes it possible for the assistance services or breakdown mechanic to locate him more quickly.
The inventors have observed that, in aforementioned cases of breakdown, certain motorists are in the incapacity of calling a breakdown mechanic or a close relation due to the fact that their GSM terminals do not include a SIM card or include a defective SIM card (i.e. a SIM card with erroneous data), or, under the effect of panic (for example in the event of a serious accident), the motorist may have blocked his SIM card by entering an incorrect password.
As such, in these conditions (GSM terminal without a SIM card), only the number 112 can be dialed. However, in certain situations, this emergency call is insufficient. Indeed, in the event of a serious accident, the motorist can have need of fast assistance. However, due to the fact that his GSM terminal does not include a SIM card, he is in the incapacity to send location information, obtained from the onboard GPS device in his vehicle. The first rescue assistance can therefore take a certain amount of time before arriving on the scene of the accident and to supply first aid to the motorist.
So there exists a real need to be able to transmit non-voice data over a transmission channel reserved for voice data. In other terms, there is a need to be able to transmit non-voice data during an emergency call with a radiocommunication terminal without a SIM card.
Different types of techniques for transmitting non-voice data over a transmission channel reserved for voice data are already known, in prior art.
Among the various types of known techniques, one technique in particular includes inserting into silent description frames (also called SID frame for “Silence Insertion Descriptor”) non-voice data and transmitting the modified SID frames over a transmission channel reserved for voice data. This known technique is in particular discussed in the Patent US 2007/0147327 (PHILIPS).
Although effective, this known technique has a certain number of disadvantages.
Conventionally, a radiocommunication terminal comprises means of voice coding enabling to generate voice frames when a voice signal is present as input to the terminal (i.e. when a user speaks) and silent frames (also called SID frames for “Silence Identity Descriptor”) when no voice signal is present as input to the terminal (i.e. when no vocal activity is detected).
A major disadvantage of the aforementioned known technique resides in the fact that the transmission of non-voice data over a communication channel reserved for voice data is conditioned by the absence of speech in terms of the user. As such, when a user is communicating with a person and wants to send this person non-voice data (for example digital photos), the user must interrupt his conversation during the entire duration of the transmission of non-voice data.
Furthermore, this known technique requires the implementation of an encapsulation mechanism (providing the insertion of non-voice data into the SID frame) that is costly in terms of calculation resources and electrical consumption.